The present invention relates to a manufacturing method for a semiconductor laser device assembled by using a die-bond paste excellent in mass productivity, and also to a semiconductor laser device.
Conventionally, there has been provided a semiconductor laser device, as shown in FIG. 7, in which a semiconductor laser chip 24 is die-bonded to a submount 23 provided on a stem 21, and further covered with a cap 25. A laser beam emitted from the semiconductor laser chip 24 is outputted through glass 26 provided in the cap 25. Then, a monitoring-use photodiode 22 on the stem 21 detects the light outputted from one side of the semiconductor laser chip 24 opposite to the glass 26 side to use the light for estimation of the intensity of the light emitted to the glass 26 side.
As another semiconductor laser device, there has also been provided an integrated semiconductor laser device called hologram laser as shown in FIG. 8. In this semiconductor laser device, a hologram device 34 is integrated with a semiconductor laser device similar in construction to that shown in FIG. 7. The semiconductor laser device using the hologram device 34 is used primarily as a light source for optical disks, in which case light emitted from a semiconductor laser chip 32 is applied to the optical disk via the hologram device 34. Then, light reflected from the optical disk is deflected and converged toward an OPIC photodetection chip 33 (photodetector in which a plurality of photodetection parts and signal processing circuits are integrated) by a diffraction effect with a hologram 34a formed on the surface of the hologram device 34, thereby detecting a signal recorded on the optical disk. The semiconductor laser chip 32 is die-bonded to a stem 31, whereas a submount for die-bonding use is omitted in FIG. 8 for simplicity' sake.
FIGS. 9A–9C are views for explaining a manufacturing method for semiconductor laser devices of FIGS. 7 and 8, where FIGS. 9A–9C depict only a portion at which the semiconductor laser chip is die-bonded. As the brazing filler metal for die-bonding, metals good at heat conduction and electrical conduction such as gold-tin alloys, solder and indium are often used, but metallic brazing filler materials are unfortunately difficult to use because of their high melting temperatures, which are generally beyond 200° C. Further, brazing filler materials using indium, which is low in melting temperature, would soften during use, causing the semiconductor laser chip to moved. Silver paste, which is an electrically conductive die-bond paste using metal, on the other hand, is easy to use even at room temperature by virtue of its paste form, and will cure at relatively low temperature of about 150° C. Even if exposed to high temperatures, silver paste, which indeed may cure, but will not soften, thus eliminating the problem that the semiconductor laser chip may be caused to move. Thus, silver paste has been widely used in recent years.
Now, a manufacturing method for a semiconductor laser device is described with reference to FIGS. 9A–9C.
First of all, as shown in FIG. 9A, a silver paste 42 is applied onto a stem 41 (or onto a submount) at room temperature.
Next, as shown in FIG. 9B, a semiconductor laser chip 43 is placed at a position where the silver paste 42 has been applied, and pressurized into a form of a semiconductor laser device. This pressurization is done in order to instantaneously purge out the silver paste that has entered into a gap between the semiconductor laser chip 43 and the stem 41 (or the submount).
Next, as shown in FIG. 9C, the semiconductor laser device fabricated at FIG. 9B is placed within thermostat 45 and then heating is performed to make the silver paste 42 cured, by which die bonding is completed. Curing conditions for silver paste in this case are set to 150° C. and about 1 hour.